Storage Settings: Allow user to trigger a volume rescan

This change allows to trigger a rescan of a volume with the next restrictions:

- Internal volumes if they are emulates
- Primary volumes
- Non-Removable volumes

Requires http://review.cyanogenmod.org/#/c/44585/

Change-Id: I42aebc9fc0d3530cf0a3efb4d2139b688707d43d
JIRA: CYAN-1391
Issue: https://jira.cyanogenmod.org/browse/CYAN-1391
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>

Conflicts:
	res/values/cm_strings.xml
Let accessibility feature instructions scroll.

Change-Id: Ie0a9eae16e8bf2ea6033a9e5e4e2c149ab4859cc
JIRA:CYAN-1531
Dont enable Wi-Fi if it's not toggleable in flight mode

Dont enable Wi-Fi if it's not toggleable in flight mode
by restoring the return which was removed by
e78c1879058571c00879f0d3e756951302adf513

Change-Id: I8ca5a3e9b3f36f148f08ce97b8a2b854bf7de21c